Christmas bombings in Nigeria blamed on radical Islamists -- the worst of which killed worshippers as they left mass -- marks a dangerous escalation in violence and risks inflaming the country's sectarian divisions, analysts said Monday.

Nigeria, Africa's most populous nation roughly divided between a mainly Muslim north and predominately Christian south, had already grown weary from years of violence claimed by the Islamist group Boko Haram.

But Sunday's attacks, also claimed by the group, have sparked fresh fear and anger. At least 40 people died nationwide, with 35 confirmed killed at St. Theresa Catholic Church in Madalla, near the capital Abuja.

"The violence is increasing both in scale and sophistication," northern-based human rights activist Shehu Sani said. "The attack on churches is to nationalise the crisis. It will instigate hitherto neutral people into the crisis."

As a result, he said, Christians may try to take revenge on Muslims.

"This is dangerous for the country," Sani said.

The government blamed the attack on Boko Haram, which has existed in varying forms since as far back as 2004. But serious questions remain over how to define the group and its aims, as well as over who supports it.

It is believed to be comprised of several factions with varying demands, including those with political links and a hard-core Islamist cell.

Conspiracy theories abound, including whether enemies of President Goodluck Jonathan, a southern Christian who faces strong opposition in the north, have backed the violence.

Analysts, however, point to Nigeria's deeply impoverished north. With so many young people out of work, distrustful of the government and without hope, it is fertile recruiting ground for such movements.

Deeply rooted corruption and a huge gap between the country's rich and poor have also fed sentiments. Nigeria is the continent's largest oil producer, but infrastructure remains woefully shoddy and most people live on less than $2 (1.5 euros) a day.

The government has been unable to stop the group, despite heavy-handed military crackdowns which analysts say only worsen the problem, causing civilians who may not otherwise sympathise with the extremists to do so.

"That is precisely the problem," said Chidi Odinkalu of the Open Society Justice Initiative.

Such crackdowns in hard-hit communities end up "driving them away from the security agencies and into the embrace of the people perpetrating this stuff," he said.

Many have suggested dialogue as a way out, but the government faces the problem of deciding with whom to talk. Boko Haram has no clear command structure and a variety of people have claimed to speak on its behalf.

The group was initially believed to be domestically focused, targeting symbols of Nigerian authority, but a suicide attack on UN headquarters in Abuja in August that killed 24 raised further concerns over its ambitions.

Whether it has ties with foreign groups, such as Al-Qaeda's north African branch, has been endlessly debated.

Diplomats say there have long been reports of Boko Haram members receiving training abroad, but that there has been no proof of operational links with outside organisations.

On Monday, the influential archbishop of Abuja, John Onaiyekan, attended a mass in memory of the victims at St. Theresa and called on Islamic leaders to take a more active role in seeking to end the violence.

He called the attacks a national tragedy.

"They should help us to identify them and help the security agencies to deal with them because they are not giving anybody a good name," he said.

"I don't even consider them Muslim fanatics since the Islamic community has told us they are not. Whatever they are, they are criminals. They are killing innocent people."

Odinkalu said the risks are many, particularly the potential to exacerbate sectarian divisions.

"This affects everybody," he said. "There is a sense of alarm in the country."

Source: AFP